Fourier transform infrared study of the protonation of the zeolitic lattice- influence of silicon - aluminium ratio and structure

W.P.J.H. Jacobs, J.H.M.C. Wolput, van, R.A. Santen, van

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Abstract

An in situ Fourier-transform infrared study is presented for the spectral region from 250 to 1400 cm-1. Using supported samples the changes for the infrared-active lattice modes after protonation are studied for zeolites A, X, L, ZK-5, mordenite and for zeolites Y with Si : Al ratios from 2.4 to 40. Protonation of the lattice results in a shift to higher wavenumbers for the asymmetric and symmetric T-O stretching modes (where T = Al or Si). These shifts are attributed to coupling between T-O lattice modes and in-plane bending modes of acidic hydroxyls. Inter-tetrahedral and intra-tetrahedral T- O stretching modes show a different coupling. Coupling between T-O lattice modes and out-of-plane hydroxyl bending modes appears to be much weaker. Protonation further results in changes of the infrared band intensities for the symmetric T-O stretching modes and for several modes in the region below 650 cm-1. The changes observed for the asymmetric T-O stretching modes are a function of the proton concentration and do not depend significantly on the lattice structure. Changes after protonation for the symmetric T-O stretching modes and especially for the modes in the region below 650 cm-1 are most sensitive to variation in zeolite structure
Original languageEnglish
Pages (from-to)1271-1276
JournalJournal of the Chemical Society, Faraday Transactions
Volume89
Issue number8
DOIs
Publication statusPublished - 1993

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